Pitmans or links for sewing machine transmissions



W. ENGEL Sept. 15, 1959 PITMANS OR LINKS FOR SEWING MACHINETRANSMISSIONS Filed June 14 1956 2 Sheets-Sheet 1 Sept. 15, 1959 w.ENGEL 2,903,909

PITMANS OR LINKS FOR SEWING MACHINE TRANSMISSIONS Filed June 14, 1956 2Sheets-Sheet 2 jm/emort' WOL Fq-A/Vg- 471/ PITMANS R LINKS FOR SEWINGMACHINE TRANSMISSIONS Wolfgang Engel, Bielefeld, Germany ApplicationJune 14, 1956, Serial No. 591,348

Claims priority, application Germany June 14, 1955 8 Claims. (Cl.74-581) The invention relates to improvements in production methods forsewing machine driving components for the purpose of decreasing theproduction costs. The increased requirements as to the number ofstitches and the noiselessness of the sewing machines compel higher wageand investment costs. These requirements could only be satisfiedheretofore by closer tolerances and increased alignment accuracy of theoperating components.

One way to obviate the alignment problem is to make individualtransmission members, particularly guide links or connection links,elastically. Since the alignment errors occur as a rule in three planes,for example, with a rotating eccentric pin, the axis of which is notparallel to the axis of rotation, it is not sufficient to replace theeyes of the link which rotate about pins or studs with leaf springswhich are screwed at the one end to the guide link and at the other tothe part to be connected because such links yield only in two places.Likewise it is not sufllcient to make a guide link elastic by making it,for example, of synthetic plastic, such as Polyamide.

The present invention relates to an arrangement for a link or pitmanwhich obtains the universal mobility or articulation by means of abridge made of an elastic material which has the axis of itslongitudinal cross section extend perpendicular to at least one of thecylindrical bores of the two linkage eyes which engage the cylindricalstuds of the parts to be connected by means of the link. To withstandonly the tractive forces the bridge is provided with a cross sectionwhich admits twisting forces; however, when subjected to thrust forces,which need to be only a fraction of the tractive or pulling forces, thebridge flexes. In order to absorb both tractive and thrust forces thebridge has adjacent its ends a substantially unchanging cross sectionwhich permits twisting forces and is of such a length as the thrustloads are greater than the bending factor.

The link or pitman may, of course, be provided with bolts or studsinstead of bores. For the elastic material it is possible to use, forexample, spring steel, artificial plastic material, rubber, or acombination of these materials. The link or pitman arrangement, inaccordance with the inventive concept may be made as a homogeneous unitor may be made of a plurality of parts. Thus, for example, when made asa single unit the device may be made of synthetic plastic. Withmulti-part embodiments of the invention the bridge encompasses the eyesof the joint. In order to insure great elasticity of the bridge in thepresence of larger tractive and thrust forces, it may be made of thinbridge leaves placed upon one another in the manner of lamination. Asmentioned hereinabove the bridge which absorbs the tractive and thrustforces should permit twisting at its ends in the proximity of the eyes;on the other hand, the bridge length which is disposed between theelastic ends must not bend as a result of the thrust loads. For thisreason the bridge may be surrounded with a coating of artificialmaterial such as plastic over this length of the bridge, or the bridgemay be secured between reini States Patent Of' 'c 2,903,909 PatentedSept. 15, 1959 forcement sheets. These reinforcement sheets are thensuitably expanded at their ends and enclose a corresponding flange atthe eyes of the pitman with tolerance therebetween in order to thusobtain the insurance against the bending end thrust loads which are toohigh.

In order to obtain an especially high elasticity of the bridge it may beprovided over that length which permits twisting with variations of itscross section, such as perforations or recesses. When making pitmans ofseveral parts the connection may be separable or solid A solidconnection, which may not be severed between the bridge and the eyes maybe made,'for example, by means of riveting, beading, dotting, orjacketing of the parts to be connected with artificial plastic orrubber. In forming the pitman of a plurality of severable parts the eyeswhich are encompassed by the bridge may suitably present a flangeagainst which the bridge is placed with its eyes and by means of anannular disc. The bridge, however, may also be secured against theflange of the linkage eyes by means of a gripping ring.

An elastic pitman of this type permits alignment compensation in threeplaces, is cheap to produce because in its production no particularalignment accuracy must be observed, it decreases the production costsof the component parts which cooperate with this pitman due to its threedimensional alignment balancing possibilities and because those partscan be made with substantially greater alignment inaccuracies as werepermissibile heretofore. It also decreases the assembly time because thereadjustment required on account of sluggish operation of the machine iseliminated and is lighter in weight as a rigid linkage, which is ofimportance in connection with high numbers of stitches.

Thus, for example, the thread lever joint of sewing machines may be madeas a pitman in accordance with the principles of the invention; at oneend of the linkage the eye is provided which is disposed with its borearound a bolt provided at the head of the arm, at the other end thelinkage is provided with a stud, which enters into the upper bore of thethread lever. The stud and the eye of the linkage are rigidly connectedwith one another by means of a bridge of flexible material. It issuitable to make the bore which surrounds the crank stud of the threadlever longer than the horizontal distance of the thread eyelet of thethread lever to this bore, in order to provide the thread lever with asecure hold when the mass forces arise which are developed by the threadlever arm.

Inasmuch as in the construction of the thread lever joint as an elasticpitman no further axial forces are developed between the stud of thethread lever joint and the upper bore of the thread lever whichsurrounds it, the stud can be secured against axial displacement bymeans of a gripping ring.

Inasmuch as the elastic pitmans are particularly flexible in thedirection of the bores they can advantageously serve as linkages betweenthe stud of the pitman of the arm shaft and the needle bar block inzig-zag sewing machines.

In the needle bar joints known heretofore the universal articulation isobtained in that the cylindrical bores co-' not have the durability asan embodiment having a cylindrical bore and cylindrical stud. For thatreason, journalling also became known where the bores were spheri-' cal.In such bores, bearing shells having a spherical outer surface arepivotally journalled. However, in order to enable the insertion of thebearing shells into the spherical I.

bore the bores may not be long. As a rule, the length of the bearingshell is smaller than the diameter of the studs of the parts to beconnected and which it surrounds.

In order to enable enlargement of the bearing shell theeyes of the jointhave already been made in several parts. All of these embodimentsrequire great accuracy possess several movable parts, and are thereforesubject to wear and noise.

In order to minimize on the one hand thepermanent bending factor of theelastic bridge and on the other hand the angle of deflection of theneedle bar it is suitable to arrange the pivot axis approximately athalf the height of the head of the arm. The location of the jointofrotation at a height between the upper joint of rotation of the needlebar block and the lower joint of rotation of the stud of the arm shafthas proven to be particularly advantageous.

A further means for decreasing the expenses are greater tolerances inbores and shafts if they do not introduce greater noise factors. It istherefore proposed in accordance with the invention to journal the armshaft elastically in the arm within the limits permissible in accordancewith sewing machine practice, particularly in the sewing machines whichare provided with elastic pitmans the advancing or progressing of whichis derived from the dog driving shaft and where the driving of the dogdriving shaft is effected from the arm shaft by means of a belt. Thearrangement of the pitman permits also the use of elastic bearingmembers for journalling the arm shaft. This elastic journal comprises abearing, the inner ring of which surrounds the arm shaft, the outer ringof which is journalled in the bore of the arm and of an intermediatelayer, for example, rubber, which rigidly connects the two rings.

The pitman arrangement is also applicable in other machines where theconditions are similar as in sewing machines.

Reference is now made to the drawings which illustrate embodiments ofthe invention and in which:

Fig. 1 shows a cross section of a thread lever link or pitman takenalong the line II of Fig. 2 in the direction of arrows;

Fig. 2 is the front view of a thread lever link;

Fig. 3 shows the front view of a modified embodiment of a thread leverlink;

Fig. 4 is a cross sectional view along lines III-III of Fig. 3 in thedirection of the arrows;

Fig. 5 is a cross section of a further embodiment of a thread lever linktaken in the direction of the arrows along line VIVI of Fig. 6;

Fig. 6 is a front view of the thread lever link in accordance with Fig.5;

Fig. 7 is a further embodiment of a thread lever link in section alongline VIIIVIII of Fig. 8;

Fig. 8 is a front view of the thread lever link in accordance with Fig.7;

Fig. 9 is a needle bar link in cross section along line XX of Fig. 10;

Fig. 10 is a front view of the needle bar link in accordance with Fig.9;

Fig. 11 is a cross section of an embodiment of a needle bar link takenalong line XIIXII of Fig. 12;

Fig. 12 is a front view of the needle bar link in accordance with Fig.11;

Fig. 13 is a sectional view of a further embodiment of a needle bar linktaken along XIVXIV of Fig. 14;

Fig. 14 is a front view of the needle bar link in accordance with Fig.13;

Fig. 15 is the front view of an arm journal and Fig. 16 is a sectionalong line XV.XV of Fig; 15 taken in the direction of arrows.

Figs. 1-8 illustrate examples of a pitman arrangement subjected merelyto tractive forces.

In Figs. 1 and 2 a thread lever link or pitman comprising severalnon-separable parts is illustrated. The bridge 2 of elastic material ofthe thread lever joint surrounds the eye 3 by means of its bore 5, aswell as the projection 4 of the stud 6. The eye 3 and the stud 6 areinseparably connected with the bridge 2 by means of the borders 7 and 8.In order to increase the elasticity the perforation 9 may be providedwhich is shown in dot and dash lines.

Figs. 3 and 4 show a thread lever link or pitman consisting of severalseparable parts. The bridge 10 of the thread lever link made of elasticmaterial surrounds the eye 11 provided with a bore 12 as well as theextension 13 of the stud 14. The bridge 10 is secured on the eye 11 andthe projection 13 against axial displacement by means of the retainingrings 15 and 16.

A further thread lever link or pitman comprising several separable partsis shown, in Figs. 5 and 6. The elastic bridge 17 rests with its uppereye against a sleeve having a projection 18 and is held by means of acover 19, for example, with three countersunk screws 20, 21 and 22. Atthe bottom the elastic bridge 17 is held with its eye at the projectionof the bolt 23 and is likewise connected with a cover 24 by means ofcountersunk screws 25, 26 and 27. A homogeneous embodiment of a threadlever link is shown by Figs. 7 and 8. The eye 28 with its bore 29, thestud 30 and the bridge 31 are all made of the same material, preferablysynthetic plastic material.

Examples of pitman arrangements which are adapted to absorb tractive andtensional forces are shown by Figs. 915. In Figs. 9 and 10 a needle barlink is illustrated which consists of several parts which are not separable. The bridge 32 of the needle bar link consisting of elasticmaterial surrounds the eye 34 which presents the bore 33 as Well as theeye 36 comprising the bore 35.

The bridge 32 is spot welded to the flanges 37 and 38 of the eyes 34 and36. This bridge is surrounded by a coating of synthetic material 39 oversuch an extent of its length as the bending tension in the presence ofthrust loads would be greater than the tractive loads in a bridge 32which is not coated. The two bridge ends 40 and 41 which are not coveredhave a cross section which permits twisting. To increase the elasticitythe bridge ends 40 and 41 may have perforations 42 and 43 Also thesolution shown in accordance with Figs. 11 and 12 may be used. Theelastic bridge of the needle bar link, which is made of severalseparable parts is connected in the same manner as described, inaccordance with Figs. 5 and 6 at the connecting locations for example,by means of screws. The bridge 44 is here provided with several closelyadjacent thin reinforcement blades 45 and 46 in the form of laminationsand is connected for example by means of countersunk screws 47 and 48.These reinforcement blades 45 and 46 are grooved at their ends 49 and 50and enclose the flange at the eyes 51 and 52 of the pitmans Withtolerances therebetween in order to achieve insurance against bending inthe event of thrust loads which are too high.

An elastic embodiment of a needle bar link is shown in Figs. 13' and 14.The eyes 53 and 54 as well as the bridge 55 consist of the samematerial, preferably synthetic plastic. The bridge 55 has reinforcements56 over such a length as bending tension in a bridge which is notreinforced would be greater under thrust loads than the thrust tension.The two ends of the bridge 57 and 58 which are not reinforced, have across section which permits twisting.

The use of the pitman arrangement in transmission components of thesewing machine permits the arm shaft 59 to be jonrnalled elastically andthus in a noise suppressing manner, if the elasticity of the journallingis within the limits permitted in accordance with sewing machine design,the dog drive shaft is driven by the arm shaft by means of a belt andthe advancing movement of the toothed head is derived from the dog driveshaft. Such an elastic type of journalling is illustrated in Figs. 15and 16. The outer ring 60 is arranged in the sewing machine arm 61 whichis shown in dash and dot lines. An intermediate layer 62 consisting ofelastic material, for example, rubber, is rigidly connected with outerring 60 and the inner ring 63 in which the arm shaft 59 is journalled.

Having now described my invention with reference to the variousembodiments shown in the accompanying drawing, I do not wish to belimited thereto, but what I desire to cover by Letters Patent of theUnited States is set forth in the appended claims.

I claim:

1. A pitman or link structure for the drive mechanism of sewing machinescomprising a pair of eye members having bores adapted to rotatablyreceive stud members and a bridge member connecting said eye membershaving a longitudinal cross sectional axis extending perpendicularlywith respect to at least one of said bores, said bridge member being ofelastic material and having a cross section adapted to yield to twistingmovements and said bores being of a length greater than the thickness ofsaid bridge adjacent said eyes.

2. A pitman or link structure for the drive mechanism of sewing machinescomprising a pair of eye members having bores adapted to rotatablyreceive stud members and a bridge member connecting said eye membershaving a longitudinal cross sectional axis extending perpendicularlywith respect to at least one of said bores, said bridge member being ofelastic material having a substantially non-varying cross sectionadjacent its ends adapted to yield to twisting forces and having an enlarged cross-section along the central portion thereof intermediate saidends to resist forces of compression.

3. A pitman or link structure for the drive mechanism of sewing machinescomprising a pair of eye members having bores adapted to rotatablyreceive stud members and a bridge member connecting said eye membershaving a longitudinal cross sectional axis extending perpendicularlywith respect to at least one of said bores, said bridge member being ofelastic material and having a cross section adapted to yield to twistingmovements, said bores being of a length greater than the thickness ofsaid bridge adjacent said eyes and said bridge encompassing said eyemembers to form a unitary structure.

4. A pitman or link structure for the drive mechanism of sewing machinescomprising a pair of eye member having bores adapted to rotatablyreceive stud members and a bridge member connecting said eye membershaving a longitudinal cross sectional axis extending perpendicularlywith respect to at least one of said bores, said bridge member being ofelastic material having a substantially non varying cross sectionadjacent its ends adapted to yield to twisting forces and of suchlongitudinal extent as the thrust loads are greater than the twistingstresses, and said bores being of a length greater than the thickness ofsaid bridge adjacent said eyes.

5. A pitman or link structure for the drive mechanism of sewing machinescomprising a pair of eye members having bores adapted to rotatablyreceive stud members and a bridge member connecting said eye membershaving a longitudinal cross sectional axis extending perpendicularlywith respect to at least one of said bores, said bridge member being ofelastic material having a substantially non-varying cross sectionadjacent its ends adapted to yield to twisting forces and of suchlongitudinal extent as the thrust loads are greater than the twistingstresses, said bores being of a length greater than the thickness ofsaid bridge adjacent said eyes and said bridge encompassing said eyemembers to form a unitary structure.

6. A pitman or link structure for the drive mechanism of sewing machinescomprising a pair of eye members having bores adapted to rotatablyreceive stud members and a bridge member connecting said eye membershaving a longitudinal cross sectional axis extending perpendicularlywith respect to at least one of said bores, said bridge member being ofelastic material and having a cross section adapted to yield to twistingmovements, said bores being of a length greater than the thickness ofsaid bridge adjacent said eyes, said bridge encompassing said eyemembers to form a unitary structure and being constituted of severalblades disposed adjacent to one another in the manner of laminations.

7. A pitrnan or link structure for the drive mechanism of sewingmachines comprising a pair of eye members having bores adapted torotatably receive stud members and a bridge member connecting said eyemembers having a longitudinal cross sectional axis extendingperpendicularly with respect to at least one of said bores, said bridgemember being of elastic material and having a cross section adapted toyield to twisting movements, said bores being of a length greater thanthe thickness of said bridge adjacent said eyes, said bridgeencompassing said eye members to form a unitary structure and beingconstituted of several blades disposed adjacent to one another in themanner of larninations and said eyes being separate parts presenting aflange against which the bridge is secured by means including annulardisks and screws.

8. A pitman or link structure for the drive mechanism of sewing machinescomprising a pair of eye members having bores adapted to rotatablyreceive stud members and a bridge member connecting said eye membershaving a longitudinal cross sectional axis extending perpendicularlywith respect to at least one of said bores, said bridge member being ofelastic material having a substantially non-varying cross sectionadjacent its ends adapted to yield to twisting forces and of suchlongitudinal extent as the thrust loads are greater than the twistingstresses and said bridge member being enclosed over said longitudinalextent in a shell of plastic material to permit twisting and insureagainst bending.

References Cited in the file of this patent UNITED STATES PATENTS803,006 Meriam Oct. 31, 1905 998,758 Eichorn July 25, 1911 1,291,743Bouwmeester Jan. 21, 1919 1,759,356 Kattwinkle May 20, 1930 1,885,976Yandell Nov. 11, 1932 1,913,513 Rossman et al. June 30, 1933 1,956,922Ingram May 1, 1934 2,338,323 Fink Jan. 4, 1944 2,532,755 Bloomfield Dec.5, 1950 2,580,781 Hotfer Ian. 1, 1952 2,758,481 Mouraviefi Aug. 14, 1956FOREIGN PATENTS 143,111 Switzerland Jan. 2, 1931 870,634 Germany July 8,1949

